This footage shows an absolutely gigantic submarine cruising silently by in Scottish waters.
The nuclear class submarine was spotted and filmed by Mike Pentland of ArgyllSeaGlass.
The vessel was surrounded by support boats and it is thought a crew change of some kind was happening.
This is not Loch Long’s first experience of submarines though.
The Loch Long Torpedo Range operated on the loch from 1912 to 1986. The abandoned Admiralty buildings, pier, and slipway remained on the west shore of the loch, opposite the village of Arrochar, until 2007, when demolition of the site began, and it was also subject to destruction by fire.
Originally an Admiralty facility, the range became the Royal Naval Torpedo Testing Station and Range, later referred to as both the Loch Long Torpedo Range, and the Arrochar Torpedo Range.
Activity at the range reached a peak during World War II, with more than 12,000 torpedoes being fired down the loch in 1944.
The Finnart Oil Terminal is located on the eastern shore of the loch, linked to the Grangemouth Refinery via a 58 miles (93 km) long pipeline.
The eastern shore is also the location of the Royal Navy’s Coulport Armament depot, part of HMNB Clyde, and the Glen Mallan jetty, linked to Glen Douglas defence munitions depot.